Assessment of the depth of anaesthesia during inhalational and intravenous induction of general anaesthesia.

Background: Tracheal intubation is one of the strongest stimuli during general anaesthesia and may result in an insufficient depth of anaesthesia. The aim of the study was to compare the clinical evaluation of the depth of anaesthesia with an evaluation using entropy during inhalational and intravenous induction of general anaesthesia.

Methods: This study involved 60 patients undergoing elective surgery under general anaesthesia. Patients were divided into two groups, group E (etomidate induction) and group S (sevoflurane induction). The systolic arterial pressure (SAP), heart rate (HR), response entropy (RE), and state entropy (SE) were determined at the following seven measurement points: before anaesthesia induction, at the loss of consciousness (LOC) point, before tracheal intubation, immediately after intubation, and 2 min., 4 min. and 6 min. after tracheal intubation. An increase in HR and/or SAP of more than 20% and/or the occurrence of lacrimation and/or perspiration in response to tracheal intubation was considered a marker of inadequate anaesthesia in the clinical evaluation. The depth of anaesthesia was considered insufficient according to entropy monitoring if the RE and SE were above 60.

Results: In clinical evaluation, insufficient anaesthesia in response to tracheal intubation was observed in all the patients in group E and in more than half of the patients in group S. At the same time, the majority of patients in both groups had entropy values that did not exceed the recommended value as an appropriate level of anaesthesia.

Conclusions: We found a discrepancy in the evaluation of the depth of anaesthesia based on clinical criteria compared with evaluations based on entropy values during both intravenous and inhalational induction of general anaesthesia.